Recent stratospheric warmings at mid-latitudes and planetary-scale wave activity

Summary Recent stratospheric warmings are herewith examined in association with the influence of long-period planetary waves. Investigations on height and time variations of geopotential and wind data obtained in the winters of 1980–87 at different tropo-stratospheric levels from messages of the radiosondes situated in the Central Europe take necessarily into account the propagation of quasi-stationary and free planetary waves which in proper conditions mutually interfere with each other. The definition and evolution of the different types of warming are connected with the structure of these waves and enable one to interpret more completely coupling phenomena among different regions of the neutal atmosphere during the most disturbed winters. Distinct spectral analysis methods permit to extract from geopotential data series prominent wave periods within 1÷3 weeks. Westerly winds in the stratosphere reach unusual amplitudes before a sudden stratospheric warming, and this amplification is seen to be in connection with transient normal modes which are able to interact even with the mean circulation of the mesosphere and lower thermosphere.     

Debris from comet Halley, comet's mass loss and age

Summary Large particles released from the nucleus of comet Halley, but undetected directly by space probes, seem to affect decisively the mass loss and mass determination of the comet, and consequently its aging. Simultaneous radar meteor observations in 1985–86 at the approaches of the comet emphasize the relatively larger proportion of long-duration echoes with respect to previous years.     

Stimulated acceleration and confinement of deuterons in focuseddischarges. II

For pt.I see ibid., vol.16, no.3, p.368-73, June 1988. Methods of increasing, by a factor greater than five, the neutron yield/short Y _n from D-D fusion reactions in a plasma focus (PF) enhance both the D⁺-ion acceleration to energy values E _d>1-8 MeV and the ion confinement in the pinch region. Nuclear activation of C and N in the (doped) filling gas of the discharge chamber and of solid targets of C and BN bombarded by the ion beam in the direction of the electrode axis (0°) confirms earlier determination of the energy spectrum of the trapped ions (dφ_t/dE∝φ_0tE ^-m) and of the ejected beam (dφ_b/dE∝φ_0bE _d^-m, m=2.5±0.5 for 0.1 MeV≲E≲3 MeV). A Thomson (parabola) spectrometer with nanosecond time resolution determines the time of emission t( E) of the beam at 0°. Ion acceleration and trapping occur within the small (filamentary) elements of the magnetic fine structure of the pinch, which can be dispersed on a relatively large confinement volume after the pinch disintegration. It has been found that φ_t/φ_b≳10-10³ for E_d≳1 MeV, depending on Y_n     

Potassium concentration differences in the vitreous humour from the two eyes revisited by microanalysis with capillary electrophoresis

This paper presents a study of the variability of potassium concentrations in the vitreous humour of the two eyes of the same body at identical postmortem interval. The study was carried out by collecting microsample amounts (50 microl) of vitreous humour and by using an original method of capillary electrophoresis with indirect detection. The electrophoretic separations were carried out in a pH 4.5 running buffer composed of 5 mmol/l imidazole, 5 mmol/l 18-crown-6 ether and 6 mmol/l alpha-hydroxybutyric acid. Detection was by indirect UVabsorption at 214 nm. Vitreous humour samples were collected from 57 medico-legal autopsies or external examinations of cases of sudden natural or violent deaths. All samples prior to analysis were diluted 1:20 with a 40 microg/ml aqueous solution of barium, the used internal standard, and finally injected by nitrogen pressure. The mean concentrations of potassium measured in the two eyes of all the cases included in the present study ranged from 4.1 to 23.5 mmol/l with the postmortem interval values varying from 7 to 144 h. A highly significant (P<0.0001) linear correlation was found between these two parameters as described by the equation: y=0.1698x+2.3587, r=0.89. The intra-eye variability of potassium concentrations was low with an average RSD of 3.89% (+/- 1.83 SD) (48 eyes, five samples per eye). No statistically significant difference was found between the potassium concentrations in the two eyes of the same subject in a group of 24 cases, excepting a single case.     

Radial and angular rotons in trapped dipolar gases

We study Bose-Einstein condensates with purely dipolar interactions in oblate traps. We find that the condensate always becomes unstable to collapse when the number of particles is sufficiently large. We analyze the instability, and find that it is the trapped-gas analogue of the "roton-maxon" instability previously reported for a gas that is unconfined in 2D. In addition, we find that under certain circumstances the condensate wave function attains a biconcave shape, with its maximum density away from the center of the gas. These biconcave condensates become unstable due to azimuthal excitation--an angular roton.     

Immobilized unfolded cytochrome c acts as a catalyst for dioxygen reduction

Unfolding turns immobilized cytochrome c into a His-His ligated form endowed with catalytic activity towards O(2), which is absent in the native protein. Dioxygen could be used by naturally occurring unfolded cytochrome c as a substrate for the production of partially reduced oxygen species (PROS) contributing to the cell oxidative stress.     

The reversible opening of water channels in cytochrome C modulates the heme iron reduction potential

Dynamic protein-solvent interactions are fundamental for life processes, but their investigation is still experimentally very demanding. Molecular dynamics simulations up to hundreds of nanoseconds can bring to light unexpected events even for extensively studied biomolecules. This paper reports a combined computational/experimental approach that reveals the reversible opening of two distinct fluctuating cavities in Saccharomyces cerevisiae iso-1-cytochrome c. Both channels allow water access to the heme center. By means of a mixed quantum mechanics/molecular dynamics (QM/MD) theoretical approach, the perturbed matrix method (PMM), that allows to reach long simulation times, changes in the reduction potential of the heme Fe(3+)/Fe(2+) couple induced by the opening of each cavity are calculated. Shifts of the reduction potential upon changes in the hydration of the heme propionates are observed. These variations are relatively small but significant and could therefore represent a tool developed by cytochrome c for the solvent driven, fine-tuning of its redox functionality.